Seeing Red • Genetics & Color Vision • Lotus Gemology

by Richard W. Hughes & John I. Koivula

Do men and women have the same ability to see red? The answer might shock you.

Few phenomena are more remarkable or complex than the sensation of color. It pervades every moment of our lives, from the red-orange of sunrise to the depths of our dreams. Even our emotions reflect the sensation of color. We "feel blue," grow "green with envy" and "red with anger." A recent discovery sheds important light on one aspect of human color vision – that of seeing red.

It has long been known that men suffer color blindness at greater rates than women. While some eight percent of men are afflicted by this malady, color blindness occurs in but 0.5% of women. Despite these numbers, we always took solace in the fact that, among color normal individuals, there were apparently no important differences between the abilities of men and women.

Not so fast, says Brian Verrelli of Arizona State University and Sarah Tishkoff of the University of Maryland. According to their study published in 2004, even men who aren't color blind may see the world differently than women. And guess who picked the short straw? That's right, guys, it's us. Seems those old stereotypes about women having a superior sense of color may be true after all.

Figure 1. Does the often-superior red sensitivity of women's color vision result from a need to distinguish edible from poisonous fruit? And should wholesale ruby dealers now be considering hiring more women? Photo: R.W. Hughes; fruit: Joan Allen

The scientists focused on a gene that allows humans to see red, a gene found only on the X chromosome. Variations in this gene can allow expanded color vision. Since men have only one X chromosome compared to the two women possess, they get one less crack at this expanded vision.

According to a recent article:

Brian Verrelli of Arizona State University and Sarah Tishkoff of the University of Maryland analyzed genetic data from 236 people from around the world. Specifically, they studied a gene on the X chromosome known as OPN1LW, which codes for a protein that detects visible light in the red spectrum. Exchange of material between this gene and a neighboring gene associated with green light leads to a high amount of genetic variation but can result in color blindness if the process goes awry. Among the study participants the researchers found 85 variants of the gene. "That's approximately three times higher than what you see at any other random gene in the human genome," Tishkoff says. "Usually it's a bad thing to have too much change in a gene, and natural selection gets rid of it. But in this case we're seeing the reverse."

Such variations have been preserved throughout evolution and are thought to be beneficial. The two scientists speculate that it might have begun in the prehistoric era, where acute color vision was of use in separating poisonous crimson berries from their edible burgundy cousins. Since women did much of the gathering (while men did the hunting), women developed better red sensitivity.

The lesson here is obvious to us: let your wife or girlfriend pick the rubies.

John Koivula is the author of the magnificent Photoatlas of Inclusions in Gemstones, Vols. 1–3, along with several other books and over 800 articles. He is currently Chief Research Gemologist at the Gemological Institute of America and is the world's foremost gem photomicrographer. John was also the scientific advisor to the famous MacGyver television series. Many of his books and enlargements of his images are available through microWorldofGems.com.